Web MIDI Linux: Omit empty values in JSON, to make id generation more robust

media/midi/midi_manager_alsa.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/midi/midi_manager_alsa.h"
 
 #include <alsa/asoundlib.h>
 #include <stdlib.h>
 #include <algorithm>
 #include <string>
@@ skipping 73 matching lines @@
 
   // If no property, look for sysattrs and walk up the parent devices too.
   while (value.empty() && udev_device) {
     value = device::UdevDeviceGetSysattrValue(udev_device, sysattr_key);
     udev_device = device::udev_device_get_parent(udev_device);
   }
   return value;
 }
 #endif  // defined(USE_UDEV)
 
+void SetStringIfNonEmpty(base::DictionaryValue* value,
+                         const std::string& path,
+                         const std::string& in_value) {
+  if (!in_value.empty())
+    value->SetString(path, in_value);
+}
+
 }  // namespace
 
 MidiManagerAlsa::MidiManagerAlsa()
     : in_client_(NULL),
       out_client_(NULL),
       out_client_id_(-1),
       in_port_(-1),
       decoder_(NULL),
 #if defined(USE_UDEV)
       udev_(device::udev_new()),
@@ skipping 284 matching lines @@
       port_name_(port_name),
       card_name_(card_name),
       card_longname_(card_longname),
       type_(type) {
 }
 
 MidiManagerAlsa::AlsaPortMetadata::~AlsaPortMetadata() {
 }
 
 scoped_ptr<base::Value> MidiManagerAlsa::AlsaPortMetadata::Value() const {
   base::DictionaryValue* value = new base::DictionaryValue();

[Takashi Toyoshima, 2015/03/23 06:17:11]

This is not introduced by this CL, but it's better to keep |value| as a
scoped_ptr here.

405: scoped_ptr<base::DictionaryValue> value(new base::DictionaryValue);
406: SetStringIfNonEmpty(value.get(), "path", path_);
...
427: return value.Pass();

-  value->SetString("path", path_);
-  value->SetString("bus", bus_);
-  value->SetString("id", id_);
+  SetStringIfNonEmpty(value, "path", path_);
+  SetStringIfNonEmpty(value, "bus", bus_);
+  SetStringIfNonEmpty(value, "id", id_);
   value->SetInteger("clientAddr", client_addr_);
   value->SetInteger("portAddr", port_addr_);
-  value->SetString("clientName", client_name_);
-  value->SetString("portName", port_name_);
-  value->SetString("cardName", card_name_);
-  value->SetString("cardLongname", card_longname_);
+  SetStringIfNonEmpty(value, "clientName", client_name_);
+  SetStringIfNonEmpty(value, "portName", port_name_);
+  SetStringIfNonEmpty(value, "cardName", card_name_);
+  SetStringIfNonEmpty(value, "cardLongname", card_longname_);
   std::string type;
   switch (type_) {
     case Type::kInput:
       type = "input";
       break;
 
     case Type::kOutput:
       type = "output";
       break;
   }
-  value->SetString("type", type);
+  SetStringIfNonEmpty(value, "type", type);
 
   return scoped_ptr<base::Value>(value).Pass();
 }
 
 std::string MidiManagerAlsa::AlsaPortMetadata::JSONValue() const {
   std::string json;
   JSONStringValueSerializer serializer(&json);
   serializer.Serialize(*Value().get());
   return json;
 }
@@ skipping 294 matching lines @@
       }
     }
   }
 }
 
 MidiManager* MidiManager::Create() {
   return new MidiManagerAlsa();
 }
 
 }  // namespace media